Just recently, when our fairly new kitchen aid dishwasher began, the house main plumbing begins to knock excessively. This only occurs when dishwasher begins/new cycle; no other appliances or faucets cause the knock. To cure the problem, I run water from another faucet in the house which eventually corrects the knock. Is this a dishwasher issue? Plumbing issue? How do you fix permanently, or call an expert?

You may have problem with the dishwasher fill valve solenoid, thanks.

John

I'm not sure what this line means: when our fairly new kitchen aid dishwasher began

This is called "water hammer". It comes from two things, valves slamming shut and unsecured pipes. The dishwasher and washer are prime candidates.

It could be the dishwasher water valve. It's definitely unsecured pipes. Sometimes there are "air columns" in the house. Draining the water system can refill the air columns.

There are commercially available water hammer aresters such as these PlumbingSupply.com - Water Hammer Arresters (Arrestors) that can be installed at the errent appliance.

In reality it's caused by shoddy plumbing workmanship.

KISS nailed it. The sudden slamming shut of the solenoid valve is giving you water hammer. Water hammer is usually recognized by a banging or thumping in water lines. The noise occurs when the flow of moving water is instantaneously stopped by a closing valve. This sudden stop results in a pressure spike behind the valve which acts like a tiny explosion inside the pipe. This pressure spike will reverberate throughout the plumbing system, rattling and shaking pipes, until it is absorbed.

Back in the 60's we were required to to put air chambers on all bath lavatories and kitchen sinks. Over time water and condensate built up in them and they must be recharged. First turn off the house at the main house shut off valve. Then open hot and cold faucets at the farthest bathroom to prevent air lock.(This is important.) You will find under each fixture little brass or chrome valves. These are called angle stops. With a small pail held under the angle stop to catch the run off look under the handle of the stop and you will see a nut with the stem running through it. This is called the bonnet packing nut. Put your wrench on it and back it off counterclockwise. Now open the stop and remove the stem and washer assembly, The stop will began to drain. When it has quit draining reassemble the stop and move on to the next one. Do this on each one of your angle stops. There will be six of them in a two bath home. When you are done, close off the faucets you have opened, turn on the water to the house, and give yourself a pat on the back.
You have just recharged your air chambers and saved yourself a hefty service call bill. Hope this helps you out and thank you for rating my reply. TOM